The UN R129/03 certification is the third phase of the development of the standard known as i-Size, which specifies safety requirements for child car seats. The R129/03 version extends the R129 standard to allow the use of three-point harness seats (without ISOFIX), making it more accessible to a wider range of vehicles. It also clarifies the rules for the use of booster seats and sets stricter criteria for side impact protection. This certification ensures a high level of safety and is currently one of the most stringent standards in force in the EU.